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Research Papers: Fluid-Structure Interaction

# Measurement of Decompression Wave Speed in Rich Gas Mixtures at High Pressures (370 bars) Using a Specialized Rupture Tube

[+] Author and Article Information
K. K. Botros1

NOVA Research & Technology Center, Calgary, AB, Canada, T2E 7K7botrosk@novachem.com

J. Geerligs

NOVA Research & Technology Center, Calgary, AB, Canada, T2E 7K7

R. J. Eiber

Consultant Inc., Columbus, OH, USA, 43220

1

Corresponding author.

J. Pressure Vessel Technol 132(5), 051303 (Aug 31, 2010) (15 pages) doi:10.1115/1.4001438 History: Received October 29, 2009; Revised February 27, 2010; Published August 31, 2010; Online August 31, 2010

## Abstract

Measurements of decompression wave speed in conventional and rich natural gas mixtures following rupture of a high-pressure pipe have been conducted. A high-pressure stainless steel rupture tube (internal $diameter=38.1 mm$ and 42 m long) has been constructed and instrumented with 16 high frequency-response pressure transducers mounted very close to the rupture end and along the length of the tube to capture the pressure-time traces of the decompression wave. Tests were conducted for initial pressures of 33–37 MPa-a and a temperature range of $21–68°C$. The experimentally determined decompression wave speeds were compared with both GASDECOM and PIPEDECOM predictions with and without nonequilibrium condensation delays at phase crossing. The interception points of the isentropes representing the decompression process with the corresponding phase envelope of each mixture were correlated with the respective plateaus observed in the decompression wave speed profiles. Additionally, speeds of sound in the undisturbed gas mixtures at the initial pressures and temperatures were compared with predictions by five equations of state, namely, BWRS, AGA-8, Peng–Robinson, Soave–Redlich–Kwong, and Groupe Européen de Recherches Gaziéres. The measured gas decompression curves were used to predict the fracture arrest toughness needed to assure fracture control in natural gas pipelines. The rupture tube test results have shown that the Charpy fracture arrest values predicted using GASEDCOM are within $+7%$ (conservative) and −11% (nonconservative) of the rupture tube predicted values. Similarly, PIPEDECOM with no temperature delay provides fracture arrest values that are within $+13%$ and −20% of the rupture tube predicted values, while PIPEDECOM with a $1°C$ temperature delay provides fracture arrest values that are within 0% and −20% of the rupture tube predicted values. Ideally, it would be better if the predicted values by the equations of state were above the rupture tube predicted values to make the predictions conservative but that was not always the case.

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## Figures

Figure 1

Schematic of the rupture tube setup

Figure 2

Schematic of the rupture tube auxiliary system

Figure 3

Test 1 pressure-time traces of the Endevco dynamic pressure transducers at the respective location identified on the right legend (top: raw data; bottom: spline smoothed)

Figure 4

Experimentally determined decompression wave speed versus pressure and comparison with GASDECOM and PIPEDECOM predictions (test 1)

Figure 5

Isentrope predicted by GASDECOM on the corresponding pressure-temperature phase diagram of the mixture composition of test 1

Figure 6

Plot of distance versus time of arrival of the decompression wave front along the rupture tube (test 1)

Figure 7

Spline smoothed pressure-time traces of test 2

Figure 8

Experimentally determined decompression wave speed versus pressure and comparison with GASDECOM and PIPEDECOM Predictions (test 2)

Figure 9

Isentrope Predicted by gasdecom on the corresponding pressure-temperature phase diagram of the mixture composition of test #2

Figure 10

Spline smoothed pressure-time traces of test 3

Figure 11

Experimentally determined decompression wave speed versus pressure and comparison with GASDECOM and PIPEDECOM predictions (test 3)

Figure 12

Isentrope predicted by GASDECOM on the corresponding pressure-temperature phase diagram of the mixture composition of Test 3

Figure 13

Spline smoothed pressure-time traces of test 4

Figure 14

Experimentally determined decompression wave speed versus pressure and comparison with GASDECOM and PIPEDECOM predictions (test 4)

Figure 15

Isentrope predicted by GASDECOM on the corresponding pressure-temperature phase diagram of the mixture composition of test 4

Figure 16

Spline smoothed pressure-time traces of test 5

Figure 17

Experimentally determined decompression wave speed versus pressure and comparison with GASDECOM and PIPEDECOM predictions (test 5)

Figure 18

Isentrope predicted by GASDECOM on the corresponding pressure-temperature phase diagram of the mixture composition of Test 5

Figure 19

Fracture toughness arrest values determined from the rupture tube tests compared with predictions (tests 1–5)

## Errata

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